1. Technical Field
The present invention relates to an absorbent article, such as a sanitary towel, a panty liner, an incontinence pad or the like, which article has two transverse end edges, two longitudinal side edges, a liquid-permeable surface layer, a liquidtight backing layer, and an absorbent core located between the liquid-permeable surface layer and the liquidtight backing layer, and also side flaps at the longitudinal side edges on both sides of the absorbent core.
2. Background of the Invention
Some modern conventional sanitary towels and similar products have side flaps. The purpose of the side flaps is to attach the article to the briefs so that it does not lie askew by being folded around the edges of the briefs in the crotch portion and attached to the outside of the briefs. Another reason for providing a sanitary towel or the like with side flaps is that the risk of leakage occurring is reduced. Leakage often occurs in sanitary towels without side flaps as a result of the edges of the briefs in the crotch area becoming turned in over the upper side of the article. This usually happens when the sanitary towel is narrower than the width of the briefs in their crotch portion. Leakage can also occur when there is insufficient time for liquid to be absorbed in the central portion of the sanitary towel, and it runs out on the surface towards and over the side edges of the article where the liquid comes into contact with the underwear. An article with side flaps assists with positioning in the briefs and reduces the occurrence of leakage. An example of a document which describes the attachment of the sanitary towel is EP 0 359 501.
On supply to the consumer, sanitary towels and similar products are often folded for packing and packed. In this context, “folded for packing” means that the side flaps are folded over the product so that they come to lie against the liquid-permeable surface layer in the central part of the product when supplied, and that the product is folded one or more times in the transverse direction or longitudinal direction in order that its size is reduced so that the product is easier to handle. Generally, the products are supplied packed, for example multipacked or individually packed. A multipacked product is characterized by a number of products lying side by side, packed in a common outer packing. An individually packed product is characterized by each individual product first being packed in its own packing which is then packed together with further individually packed products to form a larger unit in a common outer packing. Suitable materials for individual packing of the product can include, for example, an essentially liquidtight plastic film, a tissue layer or a similar thin flexible material. The common outer packing can include, for example, cardboard or plastic.
A product folded for packing is considerably smaller and significantly easier for the consumer to store and carry in a bag, trouser pocket or the like. If the products are moreover individually packed, the possibility of keeping the products hygienically is improved, so that they do not become soiled by dirt and dust when they are stored in, for example, a bag, pocket or the like.
Products with side flaps have generally been difficult to fold and pack in controlled ways during manufacture compared with products without side flaps. At a slow production rate, the side flaps of the products can be folded in a controlled manner but, at an increased production rate, this becomes difficult. The reason why the side flaps are incorrectly folded may be, for example, that the folding unit in the production machine does not function mechanically at a high rate. Another reason for the side flaps being incorrectly folded may be that the materials from which the products are made and of which the surfaces come to lie against one another when the side flaps are folded over the article have too low friction against one another. Low friction between the materials means that they do not cling to one another but slide apart.
However, the comfort to the wearer can be improved if material surfaces which will lie against the skin of the consumer have low friction. Low friction of a material means a nice, soft surface. As it is considerably more important to supply products which feel comfortable to the consumer, it is important for the problem of folding products for packing to be solved without it being necessary to forgo the quality of the material.
An incorrectly folded side flap, which projects from the product in some way, increases the likelihood of machine stoppage occurring because projecting side flaps catch on machine parts on the way through the production machine, which can lead to production being disrupted.
Another problem which can arise when the side flaps of the product are incorrectly folded is that packing the article in an individual packing is made difficult. For example, when the packing material is sealed outside the edges of the product folded for packing so as to form an individual packing, incorrectly folded side flaps can accidentally end up in the seal. A product with its side flaps caught in the seals of the individual packing is unfortunately not always detected during product control but is discovered only when the consumer is about to use the product. A product with its side flaps caught in the seals of the individual packing will be pulled apart on opening and has to be discarded by the consumer. A product with incorrectly folded side flaps moreover creates a slipshod impression which may give the consumer the impression that the functioning of the product would be worse than is actually the case.
Another problem which can arise when the side flaps are incorrectly folded is an increased risk of the protective layer on the means of attachment of the side flaps being creased or turned up from the adhesive surfaces so that the adhesive surfaces become exposed and attach themselves to surfaces other than the adhesive protective layers. Products with the adhesive surfaces of their side flaps attached to surfaces other than the protective layers may be spent and not useable by the consumer.
A further problem can arise in instances when relatively rigid material is used for the side flaps of the product. Incorrect folding of the side flaps may then become lasting, which makes it difficult to fold the side flaps around the edges of the briefs in the crotch area.
One way of reducing the problem of side flaps being incorrectly folded during production is described in, for example, EP 0 527 171. In an illustrative embodiment in EP 0 527 171, the side flaps are folded down over the liquid-permeable surface layer of the article and are held in place by a skin-friendly adhesive. One disadvantage of the illustrative embodiment described in EP 0 527 171 is the increased cost for the adhesive which is to hold the side flaps in place. Another disadvantage is that it is extremely difficult to control the strength of the adhesive so that the side flap lies sufficiently firmly against the liquid-permeable surface layer of the product. If the side flap is attached too loosely to the liquid-permeable surface layer, it will come loose during manufacture and packing. In instances when the side flap lies excessively firmly against the liquid-permeable surface layer of the product, there is a great risk that the liquid-permeable surface layer of the product and/or the side flap will be torn apart when the side flap is lifted up from the liquid-permeable surface layer. Another disadvantage is that the adhesive impairs the capacity of the product for admitting liquid into the product.
A further disadvantage of using adhesive as the means of attachment of the side flaps to the liquid-permeable surface layer of the product is that the adhesive areas which remain on the liquid-permeable surface layer after the side flaps have been lifted up from the liquid-permeable surface layer can feel uncomfortable to the consumer as the adhesive area does not have the same surface characteristics as the rest of the upper side.